Rearrangement Kimel

The Carroll rearrangement, first reported in 1940210-212, is an old and well-established versatile yet complementary variant of the Claisen rearrangement. The mechanism of this reaction was proposed in 1943 by Kimel and Cope213. With respect to the stereoselectivity, the most favorable feature of the Carroll rearrangement is the defined configuration of the double bond generated in the intermediate hydrogen-bonded enol. 

Commercial production of vitamin A, as well as other carotenoids, typically proceeds via the key intermediate pseudoinone (48) [21], which is prepared by condensation of acetone with the natural product citral. This commercial procedure has the drawback of relying on the purification of citral from lemon grass oil. In an attempt to relieve this dependence on citral, Kimel and coworkers at Hoffmann-La Roche developed an alternative fuUy synthetic route to pseudoinone (48) involving multiple Carroll rearrangements (Scheme 8.18) [22]. 

Although Carroll identified the production of cinnamyl acetoacetate (188), the detailed mechanistic rationale was later provided by W. Kimel and Arthur C. Cope in 1943. The proposal invoked a pathway similar to the Claisen rearrangement. In 1968, Hill and Synerholm proved this hypothesis to be correct and studied the stereospecificity of the reaction. ... 

Control s. Orientation control, Steric -Cope s. a. Kimel-Cope Cope rearrangement... 

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